This invention relates generally to turbomachinery, and specifically to fuel injection for a turbine combustor. In particular, the invention concerns a fuel injection system for the combustor or burner section of a gas turbine engine, for example a propulsion turbine or turbojet engine.
Gas turbine engines (combustion turbines) are built around a power core made up of a compressor, combustor and turbine, arranged in flow series with an upstream inlet and downstream exhaust. The compressor compresses air from the inlet, which is mixed with fuel in the combustor and ignited to generate hot combustion gas. The turbine extracts energy from the expanding combustion gas, and drives the compressor via a common shaft. Energy is delivered in the form of rotational energy in the shaft, reactive thrust from the exhaust, or both.
Gas turbine engines provide efficient, reliable power for a wide range of applications, including aviation and industrial power generation. Small-scale engines including auxiliary power units typically utilize a one-spool design, with co-rotating compressor and turbine sections. Larger-scale jet engines and industrial gas turbines (IGTs) are generally arranged into a number of coaxially nested spools, which operate at different pressures and temperatures, and rotate at different speeds (or, depending on design, in different directions).
Individual compressor and turbine sections in each spool are subdivided into a number of stages, which are formed of alternating rows of rotor blade and stator vane airfoils. The airfoils are shaped to turn, accelerate and compress the working fluid flow, and to generate lift for conversion to rotational energy in the turbine.
Propulsion turbines for aviation include turbojet, turbofan, turboprop and turboshaft designs. In turbojet engines, thrust is generated primarily from the exhaust. Modern fixed-wing aircraft typically employ turbofan and turboprop configurations, in which the low pressure spool is coupled to a propulsion fan or propeller. Turboshaft engines are used on rotary-wing aircraft, including helicopters.
Commercial aircraft typically trend toward higher bypass turbofan designs, in order to reduce noise and increase efficiency. Jet fighters and other supersonic aircraft tend to use lower bypass turbofans, which provide more specific thrust but may also generate more noise and have lower efficiency at low speed.
Turbojet engines are considered an older design but advanced turbojet applications are also known, including continuously afterburning and hybrid ramjet configurations for ultra-high performance aircraft and aerospace vehicles. Turbojet engines are also used in smaller-scale flight vehicles, including unmanned/unpiloted aerial vehicles (UAVs) and expendable turbojet systems for guided munitions, missiles and decoys.
Across these applications, propulsion turbine performance depends on precise control of the combustion process. In particular, combustor design is driven by the desire for higher combustion temperatures, which tend to improve thrust performance, and the need for uniform fuel/air distribution in the combustion zone, in order to increase efficiency and reduce hotspots.